Back with more of our exclusive interview with john kerry. This is his first trip back to vietnam as secretary of state. Including to the city once known as saigon, a name that will trigger a lot of memories for a lot of americans. This city was the heart of the american effort against the north vietnamese. A war that in so many ways defined john kerry. This morning, an extraordinary moment, secretary of state john kerry in the maicon delta, back on the same waters he patrolled 44 years ago as a navy swift boat commander, a tour that earned then-lieutenant kerry a silver and bronze star. What I really remember about him is the sense of everybody's commitment to doing their job, getting things done, working together effectively. It was exciting, it was scary and exhilarating, and all of kinds of emotions, sad, it was all kind of things at the same time. But what really sticks with you, there was a camaraderie and a sense of accomplishment and purpose that was very special. You saw a lot of death, but you also took a man's life, do you think about that? Yes, sometimes, sure. I mean, I think -- inevitably. But I don't get stuck there. I just, you know, I always refuse to get stuck there, kind of a purposeful decision, it happened. It is what it was. We were in a war. And it ended. My goal became the future. My gcame, how do we take that and make something better out of it? It's a goal that took him from anti-war activist. To a partnership in the senate with fellow veteran, john McCAIN, LEADING THE CHARGE TO Normalize relations with the government they fought against, and on this trip back, his first in more than ten years. Reflections on a country the u.S. Still criticizes for its human rights record, but where kerry says much has changed. The young people have a different future, where it's a marketplace, it's exciting, they have to do more on human rights, they have to do more with association. But it's gotten better in the last years. I think it's on the right track. A new vietnam, but also memories that linger, on his walk to church saturday, kerry passed the rooftop that was th sight of the last helicopter evacuation before saigon fell. You're a catholic. You went to mass this weekend here. You talked about the vietnam war, merely shaking your faith, how did you get that back? You know, I just thought about it a lot. I think I had a moment, where it just occurred to me that there still is a purpose in god's work, that defines itself sometimes differently from ways one might superficially think and, you know, you read the letters of st. Paul and you read other parts of the scriptures and it talks about suffering and it talks about adversity and, you know, I sort of began to put that in a better place, not see it so much as a, you know, a determinative god that makes every decision but rather creates a framework in which we're responsible for making things happen. Remember president kennedy's words, here on earth, god's work must truly be our own. I think that sums it up. Now, we honor our fellow americans who are currently sacrifice and serving. This week, the pentagon released the name of one service member killed in afghanistan. That's all for us today. Thanks for sharing part of your sunday with us. Check out "world news" with david muir tonight. So long from ho chi minh city in vietnam. Have a great day.

This transcript has been automatically generated and may not be 100% accurate.

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